(a) Field of the invention
The present invention concerns a headphone, and more particularly, it relates to an attachment mechanism for connecting a head band to each ear cup of headphones.
(B) Description of the prior art
In headphones, in general, it is required that the bodies of headphones fit well the ears of the user from viewpoints such as the prevention of leakage of sounds and prevention of entry of ambient noises into the ears. In order to always secure headphones to meet these requirements, the conventional headphones are arranged so that the ear cups of the headphones are allowed to make swinging and pivotal movements, with a certain degree of play, relative to the head band.
Description of the conventional typical arrangement of the means for connecting the headphones to the head band will be made by referring to FIGS. 20 and 21. FIG. 20 shows diagrammatically a longitudinal sectional view of a known arrangement for the connection of a headphone ear cup 3 to a head band 1. Within a headphone casing 11 is received a speaker 5 via a plate 4 assigned for the attachment of the speaker. A ringlike ear pad 6 is mounted at the peripheral end edge of the headphone casing 11. The head band 1 has means, such as attachment fitting 2, for connecting two such headphone casings 11 and 11 which are spaced from each other. This means 2 for connecting a headphone casing 11 to the head band 1 includes a through-hole 2a so that the head band 1 is slidably received through this through-hole 2a. This through-hole 2a has tapered portions 2c and 2c which progressively converge as this through-hole 2a goes closer to the central portion 2b of the through-hole 2a. Thus, the tapered portions 2c and 2c which oppose each other form a flaring opening angle .alpha. relative to the central portion 2b. Within the range of this opening angle .alpha., the head band 1 is adapted to incline. The connecting means 2 is supported by a horizontal shaft 2d which extends from the headphone casing 11. In such a known headphone attachment mechanism as described above, the headphone casing 11 is allowed to make free pivotal and swinging movements for a given degree of angle relative to the head band 1 depending on the amount of play provided in the attachment fitting 2, i.e. depending on the degree of angle defined by the tapered portions 2c and 2c. However, in this arrangement, the supporting point of the play is located on the part of the head band 1, and besides, the radius of rotation as measured from the supporting point 2b up to the edge of the opening 2a of the ear cup 3 is considerably lengthy. Accordingly, the relative positions between the edge of the opening 2a and the ear of the user can undergo considerably great variations depending on the angle of rotation (pivotal and swinging movement) of the headphone casing 11. For this reason, there will arise handling inconvenience for both mounting and removal of the headphones onto and from the ears of the user. In addition, the head band 1 is held only at the central portion 2b of the attachment fitting 2. As a result, there is not obtained a sufficient strength or firmness for supporting the headphones onto the ears of the user.
FIG. 21 shows another example of the known arrangement of attachment mechanism of headphones which are provided with universal rotation device. In FIG. 21, an arcuate arm 7 is rotatably coupled by a pin 8 to the lower end portion 1a of a head band 1. The opposite end portions of this arcuate arm 7 are rotatably coupled via a pair of pins 9 and 9 to the side walls of a headphone casing 11. Such an attachment mechanism as described above is most widely employed at present. The ear cup is adapted to rotate about the pins 8 provided at the coupling points between the head band 1 and the arcuate arm 7, and also at the coupling points 9 provided between the arcuate arm 7 and the headphone casing 11. In a headphone having such a known attachment mechanism as described above, the points of rotation of both the ear cup and the head band 1 are supported by pins. Accordingly, it is difficult to control the rotational friction forces at such points. As a result, there will arise unavoidable inconveniences such that the headphone casing 11 will make rotation to an amount more than necessary during the adjustment operation when mounting ear cups to the ears of the user, and that at the time of manufacture an excessively great force is required for causing a rotation of the headphone casing 11 after it has been assembled. Furthermore, this known attachment mechanism is of the arrangement designed so that the headphone casing 11 is coupled to the head band 1 by means of an arcuate arm 7 which is positioned so as to surround approximately one half of the round circumference of the headphone casing 11. As a result, the headphone will unavoidably have to assume a large external configuration.